JP2008172768A - Mobile communication terminal and mobile communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication terminal and a mobile communication method capable of improving communication quality by ensuring accuracy in measuring path timing and reception quality regardless of a moving speed. <P>SOLUTION: A mobile communication terminal 100 includes: a moving-state obtaining section 120 for obtaining the moving state of the mobile communication terminal; a path search section 131 for determining a measurement condition including any one of the number of known signals and an interval for measuring the radio signal according to the moving state obtained by the moving-state obtaining section 120; and a reception-level measuring section 135 and a demodulator 137 for performing signal processing by the use of the radio signal under the measurement condition determined by the path search section 131. The known signal is used for estimating the influence of the propagation path of the received radio signal, and has setting values that are known by both the transmitting side and receiving side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is used to estimate the influence of a propagation path of a received radio signal, receives the radio signal including a known signal whose setting value is known on the transmission side and the reception side from the radio base station, and receives the radio signal. The present invention relates to a mobile communication terminal and a mobile communication method for executing communication control based on the state of the radio signal.

  Conventionally, in a mobile communication system, time-series data of received electric field strength of a radio signal received from a radio base station in order to allow the mobile communication terminal to select an optimal radio base station according to the moving direction and moving speed of the mobile communication terminal. A method of using is known (for example, Patent Document 1).

Specifically, the mobile communication terminal selects a radio base station that is expected to obtain the optimum reception field strength based on the slope of the reception field strength specified by the time series data.
Japanese Patent No. 3481101 (page 3, FIG. 4)

  By the way, in a mobile communication system using a code division multiple access (CDMA) system, a path timing indicating a time difference with respect to a multipath reference timing separated by despreading processing and a reception level of a radio signal are measured at the mobile communication terminal. .

  In the measurement of the path timing and the reception level, it is used to estimate the influence of the propagation path of the received radio signal, and as the number of pilot symbols (known signals) whose setting values are known on the transmission side and the reception side increases, The influence of fading is suppressed, and the S / N ratio of the radio signal is improved. For this reason, the measurement accuracy of the path timing and the reception level is improved.

  On the other hand, if the number of pilot symbols used for measurement is increased, the measurement time for path timing and reception level becomes longer. For this reason, when the mobile communication terminal is moving at a high speed (for example, 100 km / h or more) (hereinafter, appropriately abbreviated as “at the time of high speed movement”), the phase of the pilot symbol to be measured is shifted due to the Doppler shift. The measurement accuracy of path timing and reception level is reduced. Such a decrease in measurement accuracy may occur particularly when a radio signal in a high frequency band such as a 2 GHz band is received and the mobile communication terminal moves at an extremely high speed (for example, 200 km / h or more).

  In addition, in order to avoid such a problem that the phase of the pilot symbol to be measured is shifted, if the measurement time of the path timing or the reception level is shortened, the mobile communication terminal is stopped or moving at a low speed (hereinafter referred to as “low speed”). The S / N ratio of the radio signal at the time of “moving” is appropriately omitted), and the measurement accuracy of the path timing is lowered.

  That is, there is a problem that it is difficult to ensure the measurement accuracy of the path timing and the reception level both when the mobile communication terminal is moving at high speed and at low speed.

  When the measurement accuracy of the path timing decreases, the mobile communication terminal cannot appropriately select the multipath used for demodulation. In addition, when the measurement accuracy of the reception level decreases, it becomes impossible to select an appropriate radio base station. For this reason, communication quality deteriorates (for example, deterioration of SIR and BLER and reduction of throughput).

 Therefore, the present invention has been made in view of such a trade-off situation, and mobile communication that can improve communication quality by ensuring measurement accuracy of path timing and reception level regardless of movement speed. An object is to provide a terminal and a mobile communication method.

In order to solve the problems described above, the present invention has the following features. First, the first feature of the present invention includes a known signal (pilot symbol P) that is used to estimate the influence of a propagation path of a received radio signal, and whose set value is known on the transmitting side and the receiving side. A mobile communication terminal (mobile communication terminal 100) that receives a radio signal (radio signal S) from a radio base station and executes predetermined signal processing based on the state of the received radio signal, the mobile communication terminal Based on the movement state acquired by the movement state acquisition unit (movement state acquisition unit 120) that acquires the movement state (for example, movement speed v) and the movement state acquisition unit (number of pilot symbols) N _S), or the measurement condition determining section for determining a measurement condition including a measurement interval (measurement interval Tm) of the radio signal (path search section 131), as determined by the measurement condition deciding section Based on the serial measurement condition, the signal processing unit for executing the signal processing using a wireless signal (reception level measuring section 135, demodulation section 137) to increase the and a.

  According to such a mobile communication terminal, measurement conditions including a measurement interval of a known signal, specifically, the number of pilot symbols or a radio signal state are determined based on the movement state of the mobile communication terminal.

  For this reason, when the mobile communication terminal moves at high speed, the number of pilot symbols used for estimating the influence of the propagation path of the radio signal may be reduced, or the measurement interval (measurement time) of the radio signal state may be reduced. it can. Further, when the mobile communication terminal moves at a low speed, the number of pilot symbols can be increased, and the measurement interval of the state of the radio signal can be extended.

  That is, according to such a mobile communication terminal, the measurement accuracy of the path timing and the reception level is ensured regardless of the moving speed, and the communication quality can be improved.

A second feature of the present invention relates to the first feature of the present invention, wherein the signal processing unit indicates a time difference of a multipath (for example, multipath MP1, MP2) with respect to a predetermined reference timing (reference timing T). The gist is to perform measurement of path timing (path timing T _P ) or measurement of the reception level relating to the radio signal and demodulation using the radio signal.

  A third feature of the present invention relates to the first feature of the present invention, wherein the movement state acquisition unit acquires a movement speed (movement speed v) of the mobile communication terminal, and the measurement condition determination unit When the movement speed acquired by the movement state acquisition unit is lower than a predetermined threshold (for example, 100 km / h), the number of the known signals used for measurement of the state of the radio signal is increased, and the movement state acquisition unit When the moving speed obtained by the above is higher than a predetermined threshold (for example, 200 km / h), the gist is to reduce the number of the known signals used for measuring the state of the radio signal.

  A fourth feature of the present invention relates to the first feature of the present invention, and is a measurement condition table (measurement condition table TB) in which the movement state, the number of known signals, and the measurement interval are associated with each other. And the measurement condition determination unit determines the measurement condition based on the measurement condition table.

 A fifth feature of the present invention is used to estimate the influence of a propagation path of a received radio signal, and a radio signal including a known signal whose set value is known on the transmission side and the reception side is transmitted from the radio base station. A mobile communication method for receiving and executing predetermined signal processing based on the received state of the radio signal, the step of acquiring the mobile state of the mobile communication terminal, and based on the acquired mobile state, Determining a measurement condition including the number of known signals or a measurement interval of the radio signal; and executing the signal processing using the radio signal based on the determined measurement condition. Is the gist.

  According to the features of the present invention, it is possible to provide a mobile communication terminal and a mobile communication method capable of improving communication quality by ensuring path timing and reception level measurement accuracy regardless of the moving speed.

  Next, an embodiment of the present invention will be described. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones.

  Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Overall schematic configuration of mobile communication system)
FIG. 1 is an overall schematic configuration diagram of a mobile communication system according to the present embodiment. As shown in FIG. 1, the mobile communication system according to this embodiment includes a communication network 10, radio base stations 11 and 12, and a mobile communication terminal 100.

  The communication network 10 is a wired communication network for connecting the radio base station 11 and the radio base station 12.

  The radio base station 11 and the radio base station 12 perform radio communication with the mobile communication terminal 100 according to a predetermined radio communication system. In the present embodiment, the radio base stations 11 and 12 and the mobile communication terminal 100 transmit and receive a 2 GHz band radio signal S according to a code division multiple access (CDMA) system. Specifically, the radio base stations 11 and 12 and the mobile communication terminal 100 are used to estimate the influence of the propagation path of the received radio signal S, and are pilots whose setting values are known on the transmission side and the reception side. A radio signal S including the symbol P is transmitted / received. In the present embodiment, the pilot symbol P constitutes a known signal.

  The pilot symbol P is a device on the receiving side, for example, mobile communication, as described in Tatsuro Masamura “Radio Technology and its Application 2 Mobile Communication” (Section 2-2-2, Maruzen Co., Ltd.). The terminal 100 is a symbol whose transmission data modulation phase is known in advance. Mobile communication terminal 100 uses the reception phase and amplitude of pilot symbol P as the reference phase and amplitude. Further, as described in the same document, the configuration of the pilot symbol P may be a time multiplexing type or a frequency multiplexing type in addition to the code multiplexing type.

  The mobile communication terminal 100 receives the radio signal S from the radio base station 11 (or the radio base station 12), and performs signal processing based on the state of the received radio signal S, for example, the radio signal S, specifically, radio The reception level L of the signal S is measured.

(Functional block configuration of mobile communication terminal)
Next, the functional block configuration of the mobile communication terminal 100 will be described. Specifically, the overall functional block configuration of the mobile communication terminal 100 and the detailed functional block configuration of the signal processing unit will be described.

  Hereinafter, portions related to the present invention will be mainly described. Therefore, it should be noted that the mobile communication terminal 100 may include a function block (such as an operation key unit) that is not illustrated or omitted in description, which is essential for realizing the function as the device.

(1) Overall Functional Block Configuration FIG. 2 is an overall functional block configuration diagram of the mobile communication terminal 100. As shown in FIG. 2, the mobile communication terminal 100 includes a wireless communication unit 110, a movement state acquisition unit 120, a signal processing unit 130, a communication control unit 140, and a battery 150.

  The wireless communication unit 110 performs wireless communication with the wireless base stations 11 and 12 according to the CDMA method. Specifically, the wireless communication unit 110 transmits and receives a wireless signal S to and from the wireless base stations 11 and 12.

  The movement state acquisition unit 120 acquires the movement state of the mobile communication terminal 100. Specifically, the movement state acquisition unit 120 acquires the movement state of the mobile communication terminal 100 by measuring or estimating the movement speed v of the mobile communication terminal 100.

  For example, the moving state acquisition unit 120 estimates the moving speed v based on the amount of change in the phase of the pilot symbol P resulting from the Doppler shift accompanying the movement of the mobile communication terminal 100. The movement state acquisition unit 120 can also detect the movement speed v based on the number of radio base stations (cells) detected within a unit time and the frequency of changing the cell in which the mobile communication terminal 100 exists. .

  Note that the movement state acquisition unit 120 may measure the movement speed v using a Global Positioning System (GPS). Furthermore, when the mobile communication terminal 100 is mounted on a vehicle such as an automobile, the movement speed v may be measured using a vehicle speed pulse of the automobile.

  The movement state acquisition unit 120 may include an acceleration sensor and an IC tag reader, and may acquire the movement state by determining whether or not the mobile communication terminal 100 is moving.

  The signal processing unit 130 executes processing related to the reception signal output from the wireless communication unit 110 and the transmission signal input to the wireless communication unit 110.

Specifically, the signal processing unit 130, as shown in FIG. 7, the multipath relative to the reference timing T (e.g., multipath MP2) performs measurements of path timing T _P that indicates the time difference. In addition, the signal processing unit 130 measures the reception level L of the radio signal S, specifically, RSCP or Ec / N0 of a pilot channel (not shown) included in the radio signal S, and demodulates using the radio signal S. And execute. Specific functions of the signal processing unit 130 will be described later.

  The communication control unit 140 executes communication control using the radio signal S. In particular, in the present embodiment, communication control is executed based on the measurement condition of the state of the radio signal S determined by the signal processing unit 130.

  Specifically, the communication control unit 140 selects a radio base station having a good reception level L, or performs a voice call outgoing / incoming process via the selected radio base station. Further, the communication control unit 140 executes control related to handover, transmission power control of the radio base station based on the measurement results of communication quality (SIR, BLER), and the like.

  The battery 150 supplies power necessary for the wireless communication unit 110, the movement state acquisition unit 120, the signal processing unit 130, and the communication control unit 140.

(2) Detailed Functional Block Configuration of Signal Processing Unit 130 FIG. 3 is a detailed functional block configuration diagram of the signal processing unit 130. As shown in FIG. 3, the signal processing unit 130 includes a path search unit 131, a RAKE combining unit 133, a reception level measuring unit 135, a demodulating unit 137, and a table storage unit 139.

  The path search unit 131 determines the measurement condition of the state of the radio signal S based on the movement state acquired by the movement state acquisition unit 120, specifically, the movement speed v. In the present embodiment, the path search unit 131 constitutes a measurement condition determination unit.

Specifically, the path search unit 131 acquires a predetermined number of pilot symbols P included in the radio signal S, calculates a despread correlation value of the radio signal S based on the acquired pilot symbols P, and performs path timing. The measurement of T _P (see FIG. 7) is performed.

In particular, in the present embodiment, the path search unit 131 uses the number of pilot symbols P used to estimate the influence of the propagation path of the radio signal S based on the moving speed v acquired by the moving state acquisition unit 120 ( The measurement conditions including the number of pilot symbols N _S ) or the measurement interval Tm of the pilot symbols P are determined. Specifically, the path search unit 131, based on the measurement condition table TB stored in the table storage unit 139, determines the number of pilot symbols N _S and a measurement interval Tm.

FIG. 8 shows an example of the measurement condition table TB according to the present embodiment. As shown in FIG. 8, the measurement condition table TB, a moving state, the number of pilot symbols N _S, and a measurement interval Tm are associated with each other. In the measurement condition table TB, three movement states from state 0 to state 2 are defined. Specifically, a stationary state or a moving state of 100 km / h or less (state 0), a high-speed moving state of 100 km / h to 200 km / h (state 1), and an ultra-high-speed moving state of 200 km / h (state 2). Is stipulated.

When the movement speed v acquired by the movement state acquisition unit 120 is lower than a predetermined threshold (for example, 100 km / h), the path search unit 131 extends the measurement interval Tm based on the measurement condition table TB (40 ms → 100 ms). ) And the number of pilot symbols _NS is increased (6 → 10).

On the other hand, the path search unit 131, the moving velocity v obtained by the moving-state obtaining section 120 is a predetermined threshold value (e.g., 200 km / h) is higher than, remove pilot symbol number _{N S} (6 → 4). The path search unit 131 may shorten the measurement interval Tm (for example, 40 ms → 30 ms) when the moving speed v acquired by the moving state acquiring unit 120 is higher than a predetermined threshold (for example, 200 km / h). ).

RAKE combining section 133, by using the path timing _{T P} and despread correlation values output from the path search unit 131 performs RAKE combining of multipaths MP1～MP3 (see FIG. 7).

  The reception level measuring unit 135 measures the reception level L of the radio signal S. The reception level measurement unit 135 measures the reception level L of the radio signal S at every measurement interval Tm notified from the path search unit 131.

  Demodulation section 137 performs demodulation processing on the received signal that has undergone RAKE combining by RAKE combining section 133.

  The table storage unit 139 stores a measurement condition table TB.

(Operation of mobile communication terminal)
Next, the operation of the mobile communication terminal 100 will be described. Specifically, (1) movement state acquisition operation, (2) path timing / reception level acquisition operation, and (3) demodulation operation will be described.

(1) Movement State Acquisition Operation FIG. 4 is a movement state acquisition operation flowchart by the mobile communication terminal 100. As shown in FIG. 4, in step S10, the movement state of the mobile communication terminal 100 is acquired. For example, the mobile communication terminal 100 estimates the moving speed v based on the amount of change in the phase of the pilot symbol P resulting from the Doppler shift accompanying the movement of the mobile communication terminal 100.

In step S20, the mobile communication terminal 100 sets the number of pilot symbols N _S and a measurement interval Tm in accordance with the moving velocity v obtained. Specifically, the mobile communication terminal 100, the moving speed v obtained, based on the measurement condition table TB (see FIG. 8), sets the number of pilot symbols N _S and a measurement interval Tm.

(2) Path Timing / Reception Level Acquisition Operation FIG. 5 is a flowchart of the path timing / reception level acquisition operation by the mobile communication terminal 100. As shown in FIG. 5, in step S <b> 110, the mobile communication terminal 100 determines the movement state of the mobile communication terminal 100. Specifically, the mobile communication terminal 100 determines whether the movement state of the mobile communication terminal 100 corresponds to the state 0 to the state 2 (see FIG. 8) based on the moving speed v of the mobile communication terminal 100. .

In step S120, the mobile communication terminal 100, based on the measurement condition table TB, acquires the number of pilot symbols _{N S} according to the determined moving state (states 0 2).

In step S130, the mobile communication terminal 100 calculates the despread correlation value of the radio signal S. Specifically, the mobile communication terminal 100, a predetermined number based on the number of pilot symbols N _S acquired in step S120 (e.g., six) using the pilot symbols P, and calculates the despreading correlation value of the radio signal S .

In step S140, the mobile communication terminal 100 measures the path timing T _P (see FIG. 7). For example, the mobile communication terminal 100 measures the time interval between the multipath MP1 and the multipath MP2.

  In step S150, the mobile communication terminal 100 acquires the reception level L of the radio signal S by executing integration of the calculated despread correlation value.

  The mobile communication terminal 100 repeats the processes of steps S110 to S150 described above at every measurement interval Tm.

(3) Demodulation Operation FIG. 6 is a flowchart of demodulation operation by the mobile communication terminal 100. As shown in FIG. 6, in step S210, the mobile communication terminal 100, by using the path timing _{T P} and despreading correlation value, executes RAKE combining multipath MP1～MP3.

  In step S220, the mobile communication terminal 100 performs demodulation processing on the received signal on which RAKE combining has been performed.

  The mobile communication terminal 100 repeats the processes of steps S210 and S220 described above at every measurement interval Tm.

(Action / Effect)
According to the mobile communication terminal 100, the state of the mobile communication terminal 100 number of pilot symbols N _S is used to estimate the influence of the propagation path of the radio signal S on the basis of the moving state (moving velocity v) or radio signal _S, The measurement conditions including the measurement interval Tm are determined.

Therefore, during high-speed movement of the mobile communication terminal 100, reduce the number of pilot symbols N _S, or can shorten the measurement interval of the state of the radio signal S Tm (measurement time). Furthermore, during low-speed movement of the mobile communication terminal 100, or increase the number of pilot symbol number N _S, or can extend the measurement interval Tm the state of the radio signal S.

That is, according to the mobile communication terminal 100, the measurement accuracy of the path timing _TP and the reception level L is ensured regardless of the moving speed v, and communication quality, specifically, SIR, BLER, and throughput can be improved. . Furthermore, when the mobile communication terminal 100 moves at a low speed, the measurement interval Tm of the state of the radio signal S can be extended, so that the consumption of the battery 150 can be suppressed.

In the present embodiment, the moving state of the mobile communication terminal 100, and the number of pilot symbols N _S, the measurement condition table TB and measurement interval Tm are associated with use. Therefore, the measurement condition of the state of the radio signal S can be easily changed by rewriting the contents of the measurement condition table TB stored in the table storage unit 139.

(Other embodiments)
As described above, the contents of the present invention have been disclosed through one embodiment of the present invention. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments will be apparent to those skilled in the art.

For example, in embodiments of the present invention described above, although the number of pilot symbols N _S and a measurement interval Tm were determined using the measurement condition table TB, the mobile communication terminal 100, using the following arithmetic expression may determine that a pilot symbol number N _S of the measurement interval Tm.
N _S = P1 / v (Formula 1)
Tm = P2 / v (Formula 2)

Here, P1 and P2 are parameters determined according to a wireless communication method used in the mobile communication system. Further, v is the moving speed (unit: km / h) of the mobile communication terminal 100. For example, 800 (unit: km / h) can be set as P1, and 8 (unit: s · km / h) can be set as P2. Furthermore, (Equation 1) and when determining the number of pilot symbols N _S and the measurement interval Tm by use of (Formula 2), may be an upper limit value and the lower limit of the number of pilot symbols N _S and a measurement interval Tm.

In the embodiment described above, the mobile communication terminal 100, the moving state obtaining operation (see FIG. 4) repeatedly in a predetermined cycle, when the number of pilot symbols N _S or measurement interval Tm is updated, the updated number of pilot symbols N _Although it has been described on the assumption that the path timing / reception level acquisition operation (see FIG. 5) is executed using _S or the measurement interval Tm, the movement state acquisition operation may be executed in step S110. In this case, since it is also set number of pilot symbols _{N S} by moving state obtaining operation in step S110, the mobile communication terminal 100 is omitted step S120.

  In the mobile communication system according to the above-described embodiment, the CDMA system is used. However, the application range of the present invention is not limited to the CDMA system. In the mobile communication system according to the above-described embodiment, the 2 GHz band radio signal S is used. However, the frequency band of the radio signal to which the present invention is applicable is not limited to the 2 GHz band.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

1 is an overall schematic configuration diagram of a mobile communication system according to an embodiment of the present invention. It is a whole functional block block diagram of the mobile communication terminal which concerns on embodiment of this invention. It is a detailed functional block block diagram of the signal processing part which concerns on embodiment of this invention. It is a movement state acquisition operation | movement flowchart by the mobile communication terminal which concerns on embodiment of this invention. FIG. 5 is a flowchart of a path timing / reception level acquisition operation by the mobile communication terminal according to the embodiment of the present invention. It is a demodulation operation | movement flowchart by the mobile communication terminal which concerns on embodiment of this invention. It is a figure which shows an example of the multipath which the mobile communication terminal which concerns on embodiment of this invention receives. It is a figure which shows an example of the measurement condition table which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Communication network, 11, 12 ... Wireless base station, 100 ... Mobile communication terminal, 110 ... Wireless communication part, 120 ... Movement state acquisition part, 130 ... Signal processing part, 131 ... Path search part, 133 ... RAKE combining part, 135: Reception level measurement unit, 137: Demodulation unit, 139: Table storage unit, 140: Communication control unit, 150: Battery, MP1 to MP3 ... Multipath, P ... Pilot symbol, S ... Radio signal, TB ... Measurement condition table , T _P ... pass timing

Claims (5)

Used to estimate the influence of the propagation path of the received radio signal, receives the radio signal including a known signal whose setting value is known on the transmission side and the reception side from the radio base station, and the state of the radio signal A mobile communication terminal that executes predetermined signal processing based on
A movement state acquisition unit for acquiring a movement state of the mobile communication terminal;
Based on the movement state acquired by the movement state acquisition unit, a measurement condition determination unit that determines a measurement condition including the number of known signals or the measurement interval of the radio signal;
A mobile communication terminal comprising: a signal processing unit that executes the signal processing using the radio signal based on the measurement condition determined by the measurement condition determination unit. The signal processing unit
Measurement of the path timing indicating the time difference of multipath with respect to a predetermined reference timing,
Or the mobile communication terminal of Claim 1 which performs the measurement of the receiving level regarding the said radio signal, and the demodulation using the said radio signal. The movement state acquisition unit acquires a movement speed of the mobile communication terminal,
The measurement condition determining unit
If the moving speed acquired by the moving state acquisition unit is lower than a predetermined threshold, increase the number of known signals used for measuring the state of the radio signal,
2. The mobile communication terminal according to claim 1, wherein when the moving speed acquired by the moving state acquiring unit is higher than a predetermined threshold, the number of known signals used for measuring the state of the radio signal is reduced. A measurement condition table in which the movement state, the number of known signals, and the measurement interval are associated;
The mobile communication terminal according to claim 1, wherein the measurement condition determination unit determines the measurement condition based on the measurement condition table. Used to estimate the influence of the propagation path of the received radio signal, receives a radio signal including a known signal whose setting value is known on the transmission side and the reception side from the radio base station, and receives the received radio signal A mobile communication method for executing predetermined signal processing based on a state,
Obtaining a movement state of the mobile communication terminal;
Determining a measurement condition including the number of the known signals or the measurement interval of the radio signal based on the acquired movement state;
And a step of executing the signal processing using the radio signal based on the determined measurement condition.

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